LongestLine

function! LongestLine()
  let longest_len = 0
  let longest_line = 0
  let cnt = 0
  for l in getline(1, '$')
    let cnt += 1
    if longest_len < len(l)
      let longest_len  = len(l)
      let longest_line = cnt
    endif
  endfor
  return longest_line
endfunction